Proposed work for the coming year will include further examination of the apical expulsion secretory mechanism so as to clarify whether the process involves an incremental release of mucus, a total loss of the mucus package, or a combination of both. The major thrust of the proposed research will center on mucus synthesis and secretion in an in vitro organ culture system. Mucus secretory mechanisms will be examined with transmission and scanning electron microscopy, and compared with that observed under in vivo conditions. Secretagogues such as carbenoxolone and prostaglandin, as well as other effectors of secretion, i.e., calcium, acetylcholine, metabolic inhibitors and cyclic nucleotides, will be used to determine their effect on exocytosis, apical expulsion, and cell exfoliation. The percent change in secreted mucus from control will be quantitated by measuring the release of radioactive labeled glycoprotein (3H or 35SO4) into the culture media.